\begin{tabular}{lcccccccc} \\\toprule
 & \multicolumn{8}{c}{Results for $\rho$} \\ 
 & \multicolumn{4}{c}{Bias} & \multicolumn{4}{c}{Std. Dev.} \\ 
& (1)& (2)& (3)& (4)& (1)& (2)& (3)& (4)\\ 
\cmidrule(r){2-5}\cmidrule(r){6-9}$N$ = 500 & 14.48 & 18.83 & 0.02 & 13.64 & 21.03 & 22.52 & 0.19 & 20.63\\ 
$N$ = 1000 & 10.82 & 13.55 & -0.00 & 9.14 & 18.76 & 19.98 & 0.14 & 17.86\\ 
$N$ = 5000 & 1.43 & 2.82 & 0.00 & 0.62 & 6.76 & 8.51 & 0.06 & 3.86\\ 
&&&&&&&& \\ 
 & \multicolumn{8}{c}{Results for $a$} \\ 
 & \multicolumn{4}{c}{Bias} & \multicolumn{4}{c}{Std. Dev.} \\ 
& (1)& (2)& (3)& (4)& (1)& (2)& (3)& (4)\\ 
\cmidrule(r){2-5}\cmidrule(r){6-9}$N$ = 500 & -0.00 & 0.01 & 0.00 & 0.01 & 0.32 & 0.33 & 0.04 & 0.31\\ 
$N$ = 1000 & 0.02 & 0.02 & 0.00 & 0.02 & 0.29 & 0.30 & 0.03 & 0.26\\ 
$N$ = 5000 & 0.01 & 0.01 & -0.00 & 0.01 & 0.12 & 0.15 & 0.01 & 0.10\\ 
&&&&&&&& \\ 
 & \multicolumn{8}{c}{Results for $\delta$} \\ 
 & \multicolumn{4}{c}{Bias} & \multicolumn{4}{c}{Std. Dev.} \\ 
& (1)& (2)& (3)& (4)& (1)& (2)& (3)& (4)\\ 
\cmidrule(r){2-5}\cmidrule(r){6-9}$N$ = 500 & -0.00 & -0.00 & -0.00 & -0.00 & 0.02 & 0.02 & 0.01 & 0.02\\ 
$N$ = 1000 & -0.00 & -0.00 & -0.00 & -0.00 & 0.01 & 0.01 & 0.01 & 0.01\\ 
$N$ = 5000 & 0.00 & 0.00 & -0.00 & -0.00 & 0.01 & 0.01 & 0.00 & 0.01\\ 
\bottomrule\end{tabular}